Year	Percent
1991	18.563
1992	16.741
1993	16.17
1994	15.015
1995	14.045
1996	13.175
1997	12.765
1998	14.295
1999	12.978
2000	12.245
2001	11.308
2002	10.674
2003	10.144
2004	9.252
2005	8.927
2006	8.635
2007	8.271
2008	7.927
2009	7.55
2010	6.882
2011	6.763
2012	6.392
2013	6.188
2014	5.712
2015	5.184
2016	4.828
2017	4.807
2018	4.702
2019	4.603
2020	4.51
2021	4.422
2022	4.342